Heretofore, it has been well known to use elastic ligatures for connecting archwires to edgewise-type brackets. An elastic ligature used for fastening an archwire in the horizontal slot of an edgewise-type bracket produces a unique "hammock effect" on the bracket. This may also be considered a centering action, as the ligature extends over and partially around the archwire at each of the mesial and distal sides of the bracket, while at the same time being hooked over the gingival and occlusal tie wing tips and there held lingual to the labial side of the archwire. Thus, this effect tends to urge the bracket to a position relative to the archwire where the archwire will be substantially centered in the archwire slot. Yet, this action caused by the "hammock effect" cannot be relied upon to positively move the bracket, and it is necessary to rely on other means to provide positive movement and control.
It has also been known to provide an edgewise-type bracket capable of allowing free crown tipping and a predetermined degree of root uprighting. This type of bracket is disclosed in copending Peter C. Kesling application Ser. No. 054,837, filed June 4, 1987, and entitled "Edgewise Bracket To Provide Both Free Crown Tipping And A Predetermined Degree of Root Uprighting". As also disclosed in this application, it is known to use an elastic orthodontic appliance in the form of a ring with enlargements for the purpose of inducing additional forces between the archwire and a bracket. While that elastic appliance is in the form of a ring and having enlargements that are intended to supplement a tipping or uprighting force transmitting device, it has been found that it is not entirely satisfactory to provide the desired supplemental force.